In his speech Thursday to the Democratic National Convention, President Obama’s mentions of China added up to just a couple dozen words, but they underscored a new and significant role the Asian power is playing in the 2012 campaign.

Obama questioned Republican challenger Mitt Romney’s lack of international experience, saying “You might not be ready for diplomacy with Beijing if you can’t visit the Olympics without insulting our closest ally.” But more than anything his discussion of China played out as a domestic economic issue. Obama spoke of competition with “the scientists and engineers coming out of China” and said the U.S. should bolster its education system so companies won’t “have to look for workers in China.”

China is a regular target in U.S. presidential campaigns, but generally it has fit squarely into the foreign policy arena—worthy of mention but rarely critical to the average voter. In the past it has largely been framed as a human rights concern, and candidates vie for who can sound tougher. Bill Clinton famously criticized George H.W. Bush in the 1992 campaign for appeasing the “butchers of Beijing,” but that election ultimately turned on economic worries.

This year, China is an economic concern itself, not just a country 6,000 miles away but seen in the specter of unemployment and a slow recovery. “The most interesting thing about China in this election season is that it’s not raised as a foreign policy issue,” says Patrick Chovanec, an economics professor at Tsinghua University in Beijing. “It’s really a domestic issue that’s related directly to jobs and prosperity in the U.S. economy.”

Romney and his running mate Representative Paul Ryan have already played up China on the campaign trail. Obama “said he’d go to the mat with China,” Ryan told supporters last month in Ohio. “Instead they’re treating him like a doormat.” The Romney campaign has accused the Obama administration of failing to challenge China over the value of its currency, the renminbi, which many economists say Beijing keeps artificially low to boost trade. Under Obama the Treasury Department has declined to label China currency manipulator, which Romney has pledged he would do on his first day in office.

“Romney has taken the offensive on China and criticized Obama,” says Chovanec, who worked for Republican commentator William Kristol and Rep. John Boehner, now Speaker of the House, in the 1990s. “I don’t think this is Obama choosing the turf. It is Romney choosing the turf and Obama on the defensive.”

On Thursday Obama argued that his administration had taken a tough approach to China. “We’ve reasserted our power across the Pacific and stood up to China on behalf of our workers,” the president said. That was likely a reference to seven cases the administration has filed with the World Trade Organization over Chinese trade practices, including a complaint in July about tariffs on large-engine U.S. vehicles. The Romney campaign has challenged some of those actions including a 2009 WTO complaint about Chinese tire exports, arguing it was done at the behest of labor unions to win support for Obama’s health care reforms.

Obama’s talk of standing up to China came just two days after Hillary Clinton left Beijing after what was her fifth visit as secretary of state. While her first trip in 2009 was full of talk about a willingness to downplay differences in order to work with China on issues like improving the global economy, this appearance was highlighted by acrimony over Beijing’s disputes with its neighbors over territorial issues including the South China Sea and the Diaoyu Islands.

She was criticized in the state media, including the Global Times, a tabloid controlled by the ruling Communist Party, which accused Clinton of “troublemaking” and said she “destroyed the atmosphere and intensified mutual distrust” between the U.S. and China. Harsh comments, but for her boss’ campaign far better than praise. Romney has been criticized just as bitterly though. Last month the official China Daily said the Republican nominee’s approach to China would lead to a “retrogression in bilateral ties and turn the region into a venue for open confrontation between China and the US.”